The present invention relates to anti-PSCA antibody compositions and methods of killing PSCA-expressing cancers cells.
In humans, prostate cancer is one of the most commonly diagnosed malignancies in males and is the second leading cause of cancer related death in men. The American Cancer Society estimates that for the year 2000, 180,400 new cases of prostate cancer will be diagnosed with 31,900 deaths from the disease. In advanced stages, prostate cancer metastasizes to the bone. While advances in early diagnosis and treatment of locally confined tumors have been achieved, prostate cancer is incurable once it has metastasized. Patients with metastatic prostate cancer on hormonal therapy will eventually develop an androgen-refractory (androgen independent) state that will lead to disease progression and death. Currently, prostate-specific antigen (PSA) is the most widely used tumor marker for screening, diagnosis, and monitoring prostate cancer. However, widespread use of PSA as a tool for screening is controversial since PSA fails to discriminate accurately between benign and malignant prostate disease.
Depending on the stage of the cancer, prostate and bladder cancer treatment involves one or a combination of the following therapies: surgery to remove the cancerous tissue, radiation therapy, chemotherapy, androgen deprivation (e.g., hormonal therapy) in the case of prostate cancer. While surgical or radiation therapy significantly improves survival in patients with early stages of the disease, the therapeutic options are very limited for advanced cases, particularly for tumor recurrences following hormone ablation. The majority of patients who undergo hormone therapy progress to develop androgen-independent disease. Currently, there is no effective treatment for the 20-40% of prostate cancer patients who develop recurrent disease after surgery or radiation therapy, or for those in whom the cancer has metastasized at the time of diagnosis. Chemotherapy has its toxic side effects, especially in elderly patients. Development of new forms of therapy especially for disease refractory to androgen deprivation is an urgent need in the management of prostatic carcinoma.
The identification of a novel cell surface antigen, prostate stem cell antigen (PSCA) has been described, see, e.g., U.S. Pat. No. 5,856,136 (SCAH2), WO 99/14328 (protein PRO232), WO 98/40403 (PSCA), WO 98/51805 (PS116) and Reiter et al. Proc. Nat. Acad. Sci. 95:1735-1740 (1998). PSCA was initially cloned from a cDNA library of a LAPC-4 xenograft from a prostate cancer patient.
PSCA is a GPI-linked molecule of 123 amino acids that is expressed on the surface of a number of cell types including prostate and bladder tumor cells. The gene is located on the myc locus on 8Q24.2 which is a region amplified in 80% of prostate cancers. PSCA shows 30% homology with SCA-2. The protein has a hydrophobic signal sequence at the first 20 amino acids of the N-terminus and a GPI-anchoring sequence at amino acid 100-123 of the C-terminus (FIG. 2 on page 1737 of Reiter et al. (1998)). There are four predicted glycoslylation sites. The cell surface protein is shed with a t1/2 of about 10 hours in culture. It has been reported that PSCA is widely over-expressed across all stages of prostate cancer, including high grade prostatic intraepithelial neoplasia (PIN), and both androgen-dependent and -independent prostate tumors. Antibodies that are able to target PSCA-expressing tumor cells in vivo and that can internalize upon binding to the cells, have not been reported.
Antibody-based therapy has proved very effective in the treatment of various cancers. For example, HERCEPTIN(copyright) and RITUXAN(copyright) (both from Genentech, S. San Francisco), have been used successfully to treat breast cancer and non-Hodgkin""s lymphoma, respectively. HERCEPTIN(copyright) is a recombinant DNA-derived humanized monoclonal antibody that selectively binds to the extracellular domain of the human epidermal growth factor receptor 2 (HER2) proto-oncogene. HER2 protein overexpression is observed in 25-30% of primary breast cancers. RITUXAN(copyright) is a genetically engineered chimeric murine/human monoclonal antibody directed against the CD20 antigen found on the surface of normal and malignant B lymphocytes. Both these antibodies are produced in CHO cells.
The present invention provides alternative methods of treating cancer that overcome the limitations of conventional therapeutic methods as well as offer additional advantages that will be apparent from the detailed description below.
The invention provides isolated anti-PSCA antibodies that internalize upon binding to PSCA on a mammalian cell in vivo. These antibodies can also target a PCSA-expressing tumor cell in vivo. In a specific embodiment, the anti-PSCA antibodies internalize upon binding to PSCA on cancer cells, including prostate cancer, urinary tract cancers (e.g., bladder cancer) and lung cancer. Provided are internalizing anti-PSCA antibodies that are monoclonal antibodies. In specific embodiments, the antibodies are 10E3, 6F8, 8D11, 5F2, 6C3, 6B8 and 10C5, produced by the hybridomas deposited under American Type Culture Collection accession number PTA-717, PTA-718, PTA-719, PTA-720, PTA-880, PTA-2265, and PTA-2264. The V region sequences of the 6F8, 8D11, 5F2, 6B8 antibodies are shown in FIGS. 12 (SEQ ID NOs. 3-9). The chimeric murine-human antibody polypeptides having the amino acid sequence of SEQ ID NO.10, SEQ ID NO.11, SEQ ID NO.12, or SEQ ID NO.13, are provided. The invention provides anti-PSCA antibodies and antibody fusion polypeptides that comprise the amino acid sequences of any one of SEQ ID NO. 1-13.
Also provided are antibodies that compete for binding to the same epitope as the epitope bound by any of the aforementioned monoclonal antibodies. In another embodiment, an isolated anti-PSCA monoclonal antibody that inhibits the growth of PSCA-expressing cancer cells in vivo, or is cytotoxic in vivo, to such cells and tumors containing such cells, is provided.
The invention also provides anti-PSCA antibodies that are conjugated to a cytotoxic agent or to a growth inhibitory agent. The antibodies are internalizing and/or growth inhibitory antibodies. The cytotoxic agent can be a toxin, antibiotic, radioactive isotope or nucleolytic enzyme. In a preferred embodiment, the toxin is a maytansinoid, more preferably the maytansinoid having the structure shown in FIG. 22.
The anti-PSCA antibodies of the preceding embodiments include intact (full length) antibodies as well as antibody fragments. The anti-PSCA antibodies of the invention include human antibodies and chimeric antibodies as well as antibody fusion polypeptides comprising at least the antibody V region sequences fused to a heterologous polypeptide. In a preferred embodiment, the anti-PSCA antibody of any of the preceding embodiments is a chimeric or human antibody. In a preferred embodiment, the chimeric antibody is a humanized antibody. The humanized anti-PSCA antibodies include humanized forms of any of the antibodies produced by the hybridomas deposited under American Type Culture Collection accession number PTA-717, PTA-718, PTA-719, PTA-720, PTA-880, and PTA-2265 and the chimeric antibodies include those having amino acid sequences of SEQ ID NO.10-13 as shown in FIG. 13. The antibodies of the invention include those produced in mammalian or bacterial cells.
The invention also encompasses a composition comprising any one of the anti-PSCA antibodies of the above embodiments, and a carrier. In one embodiment, the antibody in the composition is a human antibody or a humanized form of the monoclonal antibody produced by any one of the hybridomas deposited under ATCC accession number PTA-717, PTA-718, PTA-719, PTA-720, PTA-880, PTA-2265, and PTA-2264. In one specific embodiment, the antibody in the composition is conjugated to a maytansinoid. In a preferred embodiment, the carrier is a pharmaceutically-acceptable carrier. These compositions can be provided in an article of manufacture or a kit.
Another aspect of the invention is an isolated nucleic acid encoding any one of the anti-PSCA antibodies of the above embodiments, as well as an expression vector comprising the isolated nucleic acid operably linked to an expression regulatory sequence.
Also provided by the invention are cells that produce the above-described anti-PSCA antibodies. In one embodiment, the antibody producing cells are hybridoma cells including the specific hybridoma cells having ATCC accession numbers PTA-717, PTA-718, PTA-719, PTA-720, PTA-880, PTA-2265, and PTA-2264. In another embodiment, the cell is a bacterial cell. A host cell comprising the above-described vector is specifically provided.
The invention further encompasses a method of producing the anti-PSCA antibodies of the above embodiments, comprising culturing the cells of the above embodiments and recovering the antibody from the cell culture.
Yet a separate aspect of the invention is a method of killing a PSCA-expressing cancer cell, comprising contacting the cancer cell with an anti-PSCA antibody of any of the above embodiments, thereby killing the cancer cell. Another aspect is a method of alleviating or treating a PSCA-expressing cancer in a mammal, comprising administering a therapeutically effective amount of the anti-PSCA antibodies of the invention to the mammal. In preferred embodiments of the preceding two methods, the cancer is a prostate, bladder or lung cancer, more preferably prostate cancer and especially an androgen independent prostate cancer cell or a metastatic prostate cancer. In a preferred embodiment of these methods, the anti-PSCA antibody is a human or a humanized antibody. In another preferred embodiment, the antibody is conjugated to a cytotoxic agent such as a toxin or a radioactive isotope. Preferably, the toxin is calicheamicin or a maytansinoid such as xe2x80x9cDM1xe2x80x9d having the structure shown in FIG. 22. The method of alleviating the PSCA-expressing cancer anticipates administration of the anti-PSCA antibody in conduction with chemotherapy wherein the mammal is also receiving at least one chemotherapeutic agent. In a specific embodiment, the chemotherapeutic agent is a taxane such as paclitaxel (TAXOL(copyright)) or docetaxel, or derivatives and analogs thereof.
In a further aspect, the invention provides an article of manufacture comprising a container and a composition contained therein, wherein the composition comprises an anti-PSCA antibody of the above embodiments, and further comprising a package insert indicating that the composition can be used to alleviate or treat a PSCA-expressing cancer and in particular, prostate cancer.